Many electrical devices may be more conveniently used if they can be remotely controlled. For example, in an industrial application, such devices are mostly HVAC and lighting loads. The HVAC and lighting loads may be remotely controlled for a number of different reasons. For energy conservation reasons, some lights may be controlled by a timer. In other cases, different lighting intensity and different lighting distribution may be desirable in a single building zone, depending upon its use. Each application suggests a different lighting level and different lighting distribution and they can vary over time, due to changes in seasons and changes in daylight in a given location. Normally, changes in the control of lighting levels, distribution and timing is not done, or done very infrequently because it is inconvenient or impossible to do so with conventional control systems. Often in retrofit applications the wiring does not allow for controlling separate zones and/or lighting levels and the cost of rewiring is often prohibitive. Therefore, it is desirable to have a convenient, reliable way to remotely control individual loads or groups of loads in commercial/industrial lighting systems.
In addition to lighting systems, other devices can be conveniently remotely controlled. For example, powered gates and doors can be remotely controlled. Powered window coverings may be opened and closed, depending upon available day-lighting. Air conditioners or evaporative coolers can be activated depending on the need instead of by the circuit to which they are connected.
As electronic technology has advanced, inventors have produced a variety of control systems capable of controlling lighting and other electric loads. In order to be useful as an industrial lighting control system, there are certain requirements that must be met. A system must permit both small and large groups of lights to be controlled on command. One problem relates to the connection and communication between the controller and the lighting or HVAC loads. Most conventional connections are currently hard-wired, and trying to reconfigure the control for increased efficiency can be very complex and prohibitively expensive. Another disadvantage of any hard-wired system is that it may be very costly to change the configuration if the use pattern changes. For example, a manufacturing plant may change the configuration of its production zone layout every few years. Depending on how the different lighting zones are initially wired it may be impossible to match the old lighting zones to the new production zones thereby requiring all lights to be left on 24 hours a day using energy unnecessarily. Also, conventional, radio frequency type connection systems are known, but they have proven difficult to implement because of a combination of high noise and high attenuation found in the industrial environment and the fact that the FCC requires low signal levels. Low signal levels are subject to interference and the transmission and receiving circuitry for this type of control system is complex and relatively expensive. At present, there is no known widely deployed wireless industrial lighting control system.
In an electrical distribution system, both the controller or interface device and the load to be controlled are connected to the same powerline electrical distribution system. It therefore would be useful to use the powerline as the communication-connecting channel or means. Known, prior powerline communication systems have had difficulties employing the powerline as a communication channel because, once attenuated by the powerline circuitry, the communication signals are very small compared to the background noise. This is particularly true in the commercial/industrial three-phase environment. As is well known, between certain locations in an industrial electrical system application there will be very high attenuation of any transmitted signals. As is also well known, it has been difficult to reliably separate the highly attenuated communication signals from the background noise on the powerline, particularly in such locations.
The above-describe attenuation problem is further aggravated and complicated by the constant and unpredictable nature of changes in the noise and signal attenuation in the powerline. These changes result as various loads are connected and disconnected both inside the breaker panel to which the loads are connected and inside any of the many neighboring circuit breaker panels attached to the same mains power transformer. The noise problem has recently become much worse due to the widespread introduction of Variable Speed Drives used for controlling HVAC equipment. These drives are significant noise generators, particularly in the commercial/industrial environment. Finally, communication of control signals through the powerline circuit used for communication in an industrial application is further complicated and hindered because in the industrial environment the powerline includes all of the circuit breaker panels and loads attached to the mains power transformer. No known, practical way is available to avoid these complications.